A flat-panel CRT display basically consists of an electron-emitting device and a light-emitting device that operate at low internal pressure. The electron-emitting device, commonly referred to as a cathode, contains electron-emissive elements that emit electrons over a wide area.
The emitted electrons are directed towards light-emissive elements distributed over a corresponding area in the light-emitting device. Upon being struck by the electrons, the light-emissive elements emit light that produces an image on the viewing surface of the display.
When the electron-emitting device operates according to field-emission principles, electrically conductive seed material is commonly placed in series with the electron-emissive elements to gate the magnitude of current flow through the electron-emissive elements. FIG. 1 illustrates a conventional field-emission device, that so utilizes the seed material.
In the field emitter of FIG. 1, electrically seed (catalyst) layer 30 overlies emitter electrodes 20 provided on baseplate 10. Gate (or gate) electrodes 40, one of which is depicted in FIG. 1, are situated on dielectric layer 35 and passivation layer 45 situated on the gate layer 40 and cross over emitter electrodes 20. Electron-emissive elements 55 are situated on emitter conductive layer 30 in openings 50 through dielectric layer 35 and are exposed through corresponding openings 50 in gate electrodes 40.
Seed layer 30 is typically a blanket layer. That is, seed layer 30 extends in a continuous manner over the emitter electrodes 20 and the intervening portions of baseplate 10. Consequently, each electron-emissive elements 55 is electrically coupled through seed layer 30 to each other element 55. In the prior art device shown in FIG. 1, the electron emissive elements are a group carbon based filaments.
The catalyst layer 30 is normally a conductive material that is layer 30 effectively does not electrically isolate each group of elements 55 from each other. Thus, there could be a kind of intercoupling of electrons emissive elements 55 through layer 30. That means electron emission from a group of elements 55 would have an effect on the other group of element 55. A degradation or an emitting of one group of elements 55 usually means other groups of elements 55 would have an effect on the emitting of other groups of element 55.
The non-uniformity of deposition, patterning and etching of each process causes undesirable non-uniformity of the feature of electron emission elements 55. The non-uniformity of the electron emission elements creates a situation where the elements 55 have different threshold voltage for electron emission. Thus, most of elements 55 would not start to emit electrons at the same time.
Because of the intercoupling provided by catalyst layer 30, a few of the groups of the elements 55 that would have low value of voltage could become the primary source of electron emitting for the entire group in the display device rather than emitting electrons from most of the groups of elements 55. Thus, those elements 55 that act as a primary electron emitting source could result in the emitter degradation.
Furthermore, the field emitter device shown in FIG. 1 has a blanket resistor layer the overlies the emitter electrode 20. The blanket resistor layer 25 electrically couples each electron-emissive element 55 to each other. The resistance of layer 25 is sufficiently high that the inter-coupling of electron-emissive elements 55 has little effect on the display operation. In fact, layer 25 is normally of such high resistance that layer 25 effectively electrically isolates each element 55 from each other. However, there is still some undesirable leakage current flows between elements 55 due to the inter-coupling provided by layer 25.
Because layer 25 is a blanket layer that covers the emitter electrode 20 and extends in a continuous manner over intervening portions of the base plate including pad region 60 (FIG. 1B), portions of the resistor layer 25 in pad region 60 must be removed during masking step subsequent to the deposition of layer 25. This is costly, time consuming and results in an inefficient manufacturing fabrication of the display device.
It is therefore desirable to have a resistor layer that provides resistance at selected areas along base plate 10 but does not itself electrically interconnect these areas.
It is also desirable to have a pattern resistor layer along the base plate 10 upon which the carbon based emitter electrons are disposed and treated that reduces the number and/or complexities of steps conventionally required to fabricate the field emitter structure.
It is also desirable to configure the resistor layer in such a way that underlying emitter electrodes be externally electrically accessible along their upper surfaces without the necessity of performing a separate etching operation to cut openings through the seed layer. Furthermore, it is preferable to provide a suitable pattern in the resistor layer without employing any additional masking steps beyond those used for patterning other components in the field emitter.